The semiconductor device industry has a market driven need to reduce the cost of devices used in products such as processor chips, mobile telephones, and memory devices such as dynamic random access memories (DRAMs). Semiconductor companies generally rely on the ability to manufacture semiconductor products at several fabrication facilities, or use parallel process lines and different process equipment to meet demands. Different device geometries are used to obtain devices with different performance specifications. Variations in processes can result in wafer-to-wafer and die-to-die variations in device performance. Temperature and supply voltage variations can have the same result. Sometimes the variations are large enough that the end device operates outside the design specification rending it unusable for an intended application. More product must be generated to account for the loss, adding to costs. Process and related variations and differences in operating conditions have created a need for control circuitry.